Heat exchanger having twisted multiple passage tubes



' Dec. 17, 1968 I I R. w. FINK 3,416,500

HEAT EXCHANGER HAVING TWISTED MULTIPLE PASSAGE TUBES Filed Jan. 23, 1967 m now Rfww d, @M

United States Patent O 3,416,600 HEAT EXCHANGER HAVING TWISTED MULTIPLE PASSAGE TUBES Robert W. Fink, Nashville, Tenn., assignor to Whirlpool Corporation, a corporation of Delaware Filed Jan. 23, 1967, Ser. No. 610,943 12 Claims. (Cl. 165-175) ABSTRACT OF THE DISCLOSURE A heat exchanger including flat tubes having twisted end portions arranged to have the flat extent thereof par-allel to the axis of elongated headers to which the ends are connected. There is provided a 180 twist in an intermediate portion of the tube with the tube being internally divided into at least two through passages whereby the 180 twist permits one passage to be ydisposed foremost in one portion of the tube and rearmost in lanother portion of the tube, and the other passage disposed rearmost and foremost respectively -in these portions relative to a flow of heat exchange fluid past the tube in a direction parallel to the flatwise extent thereof, thereby to equalize heat transfer conditions in fluids flowing through the respective passages.

SPECIFICATION This invention relates to heat exchangers and in particular to tube type heat exchangers.

In one form of heat exchanger such as used in air conditioners, the condenser comprises a serpentine tube having its opposite ends connected to inlet and outlet manifolds. In one form of such a `serpentine tube, the tube is elongated -in cross-section and provided with a plurality of internal dividing walls so as to define therein a plurality of fluid ow passages. Such tubes have heretofore had the disadvantage of difliculty of connection of the opposite ends thereof to the normally cylindrical manifolds as the flatwise vdimension of the tube rnay well be larger than the diameter of the manifold. Another problem arising in the use of such divided, multi-flow passage tubes is the nonuniform heat exchange conditions relative to the different flow passages. Thus, fluid flowing in the foremost passage relative to the direction of the heat exchange fluid being flowed against the outside of the tube parallel to the flatwise extent of the tube will have maximum heat exchange as a result of the external fluid first contacting this portion of the tube. As some thermal t-ransfer occurs at this point, this fluid when flowing past the rearmost portion of the tube will have a lesser heat exchange with the fluid flowing in the rearmost passage of the tube. The present invention comprehends an improved heat exchanger construction eliminating the disadvantages of the above `discussed conventional flat tube heat exchangers in a novel and simple manner.

Thus, a principal feature of the present invention is the provision of a new and improved heat exchanger apparatus.

Another feature ofthe invention is the provision of such a heat exch-anger apparatus including a tubular duct having an elongated cross-section and defining a fluid flow passage therethrough, an elongated header defining a hollow interior, the header having its longitudinal extent angularly related to the direction of cross-section elongation of the duct, and means for connecting the flow passage of the duct to the interior of the header for lluid flow therebetween comprising an en-d portion of the duct connected to the header and twisted to have the elongated cross-section direction thereof at the connection thereof to the header parallel to the longitudinal extent of the header.

A further feature of the invention is the provision of such a heat exchanger apparatus including means for flowing a heat exchange fluid through a space in a preselected direction, tubular means defining a plurality of side-byside ducts defining la plurality of fluid flow passages, the tubular means extending across the space and provided with a portion twisted 180, one of the ducts at one side of the portion being the most upstream duct relative to the heat exchange fluid flow direction and at the opposite side of the portion by the `most downstream duct and a second of the ducts at the one side of the portion being the most downstream duct 'and at the opposite side of the portion being the most upstream duct.

Still another feature of the invention is the provision of such a heat exchanger apparatus wherein the tubular means defines a serpentine configuration.

Other features and advantages of the invention will be apparent from the Ifollowing description taken in connection with the accompanying drawings wherein:

FIGURE 1 -is a top plan view of a heat exchanger embodying the invention;

FIGURE 2 isa front elevation thereof;

FIGURE 3 is an enlarged fragmentary vertical section thereof taken substantially along the line 3 3 of FIG- URE l;

FIGURE 4 is an enlarged fragmentary front elevation with portions thereof broken away to facilitate illustrat-i-on of the invention;

FIGURE 5 is a fragmentary side elevation of a modified form `of heat exchanger apparatus embodying the invention;

FIGURE 6 is a diagrammatic front eleva-tion of la portion of the flat duct at 180 twist therein illustrating the reversal of the internal flow passage disposition; and

FIGURE 7 is an enlarged transverse section of the flat tubular duct.

In the exemplary embodiment of the invention as disclosed in FIGURES 1 through 4 and 7 of the drawing, a heat exchanger apparatus generally designated 10 is shown to comprise a condenser formed of a plurality of flat tubular ducts 11 each connected at one end to an inlet header or manifold 12 and at the opposite end to an outlet header or manifold 13. The flat tubular ducts 11 have a substantially elongated cross-section, as best shown in FIGURE 7, wherein the elongated extent -is over twice the width and in the illustrated embodiment is over four times the width. The duct or tube 11 may be generally rectangular in cross-section and is provided with at least one, and herein three, divider walls 14, 15 and 16 defining interiorly of the duct a plurality of passages, herein passages 17, 1'8, 19' and 20.

The headers 12 and 13 herein comprise relatively small diameter circularly tubular headers. As best seen `in FIG- URES 1 and 3, the opposite ends of the ducts 11, illustratively ends 21 and 22 thereof, are twisted approximately from the flatwise extent of the mid-portion of the duct so as to define distal portions 23 having their flatwise extent parallel to and aligned with the axis 24 of the header. As illustrated in FIGURES 3 and 4, the distal portion 23 is sealingly connected to the wall of the header and projects inwardly therethrough to provide communica. tion between the hollow interior 25 of the headers and the flow passages 17-20 of each duct. As shown, the elongated extent of the ducts 11, i.e. the flatwise extent, -may be substantially greater than the diameter of the tubular headers, while yet the distal ends 23 maybe readily sealingly connected to the header wall in correspondingly elongated slots 26 therein extending parallel to the axis 24. The ducts 11 and headers 12 and 13 may be formed of a suitable metal such as aluminum and the duct ends 23 may be secured in the slots 26 by suitable means such as brazing, soldering, welding, or with the use of an appropriate adhesive material.

Each duct 11 may be arranged in a serpentine configuration between its opposite ends 21 and 22, and in the illustrated embodiment each duct is provided with two turns defining three parallel spaced runs, illustratively, runs 27, 28 and 29. In addition, each run is formed into a U-shaped configuration, as shown in FIGURE 1, and fins 30 are provided extending between the respective runs, as shown in FIGURES 2 and 3, and suitably joined to the ducts 11 to provide improved heat transfer Abetween the ducts 11 and a heat transfer fluid flowed thereagainst in a direction perpendicular to the paper as shown in FIGURE 2. The top of the heat exchanger comprises a flat sheet metal plate 31 and the bottom comprises a corresponding flat sheet metal plate 32 for confining the heat exchange fluid therebetween and in a path generally parallel to the flatwise extent of the duct turns 2729.

The flow of the heat exchange fluid as in the direction of the arrows 33 shown in FIGURE 3 against the ducts 11 effects a heat exchange transfer relative to fluids flowing through the passages within the ducts 11 between the headers 12 and 13. It will be seen, however, that the foremost passage (relative to the direction of flow of the heat exchange fluid externally thereagainst) is the foremost passage in each of the three runs 27, 28 and 29, and the rearmost passage 17 is the rearmost in each of these runs. This may cause a limitation in the efficiency of heat transfer in that the maximum heat transfer occurs between the heat exchange fluid and the fluid in foremost passage 20 and a reduced heat exchange occurs relative to the fluid in the rearmost passage. To avoid this, a modified apparatus generally designated 110 may be provided, as shown in FIGURES 5 and 6, wherein a 180 twist portion 134 is provided intermediate the opposite ends 121 and 122 of the duct. Where a serpentine duct configuration is provided between the two headers 112 and 113, the twist portion 134 may be provided at the end of one pair of runs, such as runs 127 and 128. Thus, as illustrated in FIGURE 6, whereas the foremost passage is passage 120 in run 127, passage 120 becomes the rearmost passage in run 128 and the rearmost passage 117 in run 127 becornes the foremost passage in the run 128. Thus, for a substantial portion of the extent between the headers 112 and 113, a reversal in the disposition of the respective flow passages in duct 11 is provided, thereby providing improved heat transfer efficiency in the heat exchanger 110.

If it is desired to provide the twist portion 134 at the center of the duct 11, i.e. half-way Ibetween the ends 121 and 122 which would be in the center of run 128, to cause the respective flow passages to be positionally reversed for substantially equal distances at the opposite sides of the twist portion, this may be effected with concurrent omission of the fins 30 at this point. Other than as discussed above, the structure of heat exchanger apparatus 110 is similar to the structure of heat exchanger apparatus 10, elements of apparatus 110 being identified by similar reference numerals applied to similar elements of heat exchanger 10, but one hundred higher.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes therefore, in the construction and arrangement may be rnade without departing from the spirit and scope of the invention as defined in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Heat exchanger apparatus comprising: means for flowing a heat exchange fluid in a preselected direction through a space; a preformed serpentine tubular duct extending across said space, said duct being elongated in cross-section parallel to said preselected direction and defining a fluid flow passage therethrough whereby improved heat exchange between fluid flowed through said space and fluid flowed through said passage is obtained, said duct including opposite end portions; a pair of elongated headers, each header defining a hollow interior and a slot opening to the interior and extending parallel to the longitudinal extent of the headers, each said header having its longitudinal extent angularly related to the direction of cross-section elongation of said duct; and means connecting said end portions of said preformed duct respectively to said headers for fluid flow therebetween, said end portions being turned relative to the elongated cross-section of the duct therebetween to have the elongated cross-section direction of said end portions at the connection thereof to the headers parallel to said longitudinal extent of the headers.

2. The heat exchanger apparatus of claim 1 wherein said longitudinal extent of each header is perpendicular to said direction of cross-section elongation of the tubular duct between said end portions.

3. The heat exchanger apparatus of claim 1 wherein said duct and portions are received in said header slots.

4. The heat exchanger apparatus of claim 1 wherein said tubular duct defines a plurality of parallel fluid flow passages therethrough and said duct is turned at a portion intermediate said ends to alter the disposition of said passages in a direction parallel to the direction of elongation of said duct.

5. The heat exchanger apparatus of claim 1 wherein each said header defines a longitudinal axis and said duct end portions are twisted about axes respectively perpendicularly intersecting said header axes.

6. The heat exchanger apparatus of claim 1 wherein the elongated extent of said tubular duct is greater than the extent of each of said headers parallel thereto.

7. The heat exchanger apparatus of claim 1 wherein the tubular duct and headers are preformed of similar metal.

8. Heat exchanger apparatus comprising: means for flowing a heat exchange fluid through a space in a preselected direction; and tubular means defining an integral plurality of side-by-side ducts defining a plurality of fluid flow passages, said tubular means extending across said space and provided at a point intermediate the ends thereof with a portion twisted one of said ducts at one side of said portion being the most upstream duct relative to said heat exchange fluid flow direction and at the opposite side of said portion by the most downstream duct and a second of said ducts at said one side of said portion being the most downstream duct and at said opposite side of said portion being the most upstream duct.

9. The heat exchanger apparatus of clai-m 8 wherein said tubular means is elongated in cross-section parallel to said heat exchange fluid flow direction.

10. The heat exchanger apparatus of claim 8 wherein the tubular means defines a serpentine configuration transverse to said heat exchange fluid flow direction.

11. Heat exchanger apparatus comprising: means for flowing a heat exchange fluid through a space in a preselected direction; and tubular means defining an integral plurality of side-by-side ducts defining a plurality of fluid flow passages, said tubular means extending across said Space and provided at a point intermediate the ends thereof with a portion twisted 180, one of said ducts at one side of said portion being the most upstream duct relative to said heat exchange fluid flow direction and at the opposite side of said portion by the most downstream duct and a second of said ducts at said one side of said portion being the most downstream duct and at said opposite side of said portion being the most upstream duct, said tubular means defining a serpentine configuration including an odd number of runs, said twisted portion connecting the end of a pair of said runs.

12. Heat exchanger apparatus comprising: 'means for flowing a heat exchange fluid through a space in a preselected direction; and tubular means defining an integral plurality of side-by-side ducts defining a plurality of fluid flow passages, said tubular means extending across said space and provided at a point intermediate the ends thereof with a portion twisted 180, one of said ducts at one side of said portion being the most upstream duct relative to said heat exchange fluid ow direction and at the opposite side of said portion by the most downstream duct and a second of said ducts at said one side of said prtion 'being the most downstream duct and at said opposite side of said portion being the most upstream duct, said tubular means being elongated in cross-section parallel to said heat exchange uid ow direction, and said apparatus further including an elongated header having its longitudinal extent angularly related to said heat exchange fluid ow direction, and means for connecting said ducts to said header for uid ow therebetween comprising an end portion of said tubular means twisted to have its elongated cross-section direction at the connection thereof to the header parallel to said longitudinal extent of the header.

References Cited FOREIGN PATENTS 6/ 1945 Great Britain. 7/ 1960 France.

ROBERT A. OLEARY, Primary Examiner. M. A. ANTONAKAS, Assistant Examiner.

U.S. C1. X.R. 

